Patent Application
20240176295
This application claims priority of European patent application No. EP22209734.7 filed Nov. 25, 2022, the content of which is hereby incorporated by reference herein in its entirety.
The invention concerns a transmission mechanism for an automatic winding chain. The invention also concerns an automatic winding chain including a transmission mechanism of this kind. The invention also concerns a timepiece movement including a transmission mechanism of this kind or an automatic winding chain of this kind. The invention finally concerns a timepiece including a transmission mechanism of this kind or an automatic winding chain of this kind or a timepiece movement of this kind.
Reversing systems employing pawl freewheels are today widely used in horology for automatic winding of a barrel spring. Pawl freewheels constitute a reliable and robust solution enabling the benefit of:
For the dead angle of the reversing system relative to the oscillating mass to be as low as possible, it is preferable to arrange the reversing system as close as possible to the latter. However, because of the high transmission ratio of the automatic winding chain, an arrangement of this kind generates extreme mechanical loads on the wheels of the reversing system during manual winding. In fact, the closer the reversing system is to the oscillating mass, the higher the transmission ratio from the winding stem and therefore the faster the wheels forming part of the reversing system turn during manual winding. With an arrangement of this kind the rotation speed of the wheels of the reversing system can generate oscillation of the pawls at a frequency greater than 3 000 Hz, or even greater than 5 000 Hz. These extreme loads are liable to degrade the pawl freewheels through premature wear of the pawls and/or the complementary teeth. Moreover, during manual winding oscillation of the pawls of the pawl freewheels closest to the oscillating mass generate a high torque transmitted to the winding stem. Because of this, the torque that the kinematic systems have to withstand is also higher, which can also cause premature ageing of the various wheel sets.
From a sensory point of view, these loads can generate a sensation of scraping on the winding stem and a disagreeable noise for the user of the watch.
Freewheel solutions are known enabling disengagement of the automatic winding chain during manual winding which alleviates the premature wear of the reversing system. Given that disengagement is effected only during manual winding, that is to say by the effect of a torque exerted by the user, the freewheel known from the prior art is of simpler design and offers lower performance than those that constitute a reversing system. Said freewheel may have a rudimentary shape with one or more leaf springs or pawls adapted to cooperate by obstacle with a toothed wheel and able to generate a high disengagement torque. It is generally disposed as close as possible to the barrel ratchet so as to prevent too high a rotation speed during manual winding and thus to prevent premature wear.
Because of its relatively simple design, the freewheel known from the prior art can generate the following disadvantages:
In Théorie d′horlogerie (Reymondin et al., éditions de la Fédération des Écoles Techniques, 1998), disengaging an automatic winding chain during manual winding is described. A freewheel is arranged in a ratchet drive mobile. This freewheel includes, for example, a spring with arms secured to a pinion, intended to cooperate with a ratchet drive wheel around the pinion. The torque needed to disengage this type of freewheel may be relatively high. This high disengagement torque may constitute a problem if it is greater than the reversing system disengagement torque simply because the freewheel will be only partially or not at all functional. In fact, it might not disengage except in the case of severe wedging or scraping of the reversing system and would then inevitably generate variations of noise and of sensation on the winding stem potentially uncomfortable for the user. Disposing this freewheel near the ratchet also implies that the torque that it has to withstand during automatic winding is high.
Disengaging an automatic winding chain using an elastic pawl is also described in the document CH277730A. As in the previous solution, this freewheel is arranged in a ratchet driver engaged with a ratchet.
The document EP2392975A2 discloses a particular construction of a freewheel with elastic pawls intended to cooperate with internal teeth. The arrangement of the freewheel in the automatic winding chain remains similar to the previous solutions described.
The document EP2634650A2 discloses a solution using a freewheel arranged in a mobile of a Pellaton-type reversing system. This enables disengagement of the reversing system during manual winding with a freewheel functioning by obstacle.
The object of the invention is to provide a transmission mechanism solving the problems mentioned above and enabling improvement of the transmission mechanism known from the prior art. In particular the invention proposes a transmission mechanism enabling optimisation of performance and what the user feels during manual winding.
A transmission mechanism according to the invention is defined by point 1 below.
Embodiments of a transmission mechanism according to the invention are defined by points 2 to 7 below.
An automatic winding chain or an automatic winding module according to the invention is defined by point 8 below.
Embodiments of an automatic winding chain or an automatic winding module according to the invention are defined by points 9 and 10 below.
A timepiece movement according to the invention is defined by point 11 below.
Embodiments of a timepiece movement according to the invention are defined in points 12 and 13 below.
A timepiece according to the invention is defined by point 14.
The appended drawings represent by way of example one embodiment of a timepiece according to the invention.
A first embodiment of a timepiece 400 is described in detail hereinafter with reference to
The timepiece 400 is for example a watch, in particular a wristwatch. The timepiece 400 includes a timepiece movement 300 intended to be mounted in a timepiece case in order to protect it from the external environment.
The timepiece movement 300 is an automatic movement or a hybrid movement.
The timepiece movement 300 includes an automatic winding chain 200. This automatic winding chain may be included in an automatic winding module 250 mounted on the rest of the timepiece movement, in particular an automatic winding module 250:
The automatic winding chain 200 includes a transmission mechanism 110.
The transmission mechanism 110 includes a series assembly of:
By “freewheel functioning by wedging” is meant a freewheel the engagement function of which is achieved by wedging or jamming caused by the friction of rolling elements such as balls or rollers or runners, or sliding elements such as cams or shape runners.
By “unidirectional coupling functioning by obstacle” is meant a reverser as described in particular on pages 178 and 179 of the book “Théorie d′horlogerie” (Reymondin et al., éditions de la Fédération des Écoles Techniques, 1998), that is to say:
By “freewheel functioning by obstacle” is meant a freewheel the engagement function of which is assured by elements constituting obstacles to one another (and therefore functioning even in the absence of friction between these elements).
By “freewheel” is meant an assembly comprising:
The reverser 50 is a direction reverser or a reversing system 50 and enables conversion of:
To this end the winding mobile mass is mechanically connected to an input of the reverser and the unidirectional movement in rotation is obtained at an output of the reverser.
The first freewheel 40 enables disengagement of the reverser 50 during manual winding, that is to say when a user arms or winds the barrel 20 by exerting action on a manual winding member, for example by applying a movement in rotation to a stem 10 via a crown. This disengagement enables decoupling or unfastening of the reverser and of the part of the system downstream of the first freewheel.
The automatic winding chain or automatic winding kinematic system 200 enables arming or automatic winding of a barrel 20 thanks to transmission of energy from the movements of the winding mobile mass 60.
The barrel 20 can also be wound manually by a winding stem 10 via a manual winding kinematic chain 100.
In the embodiment represented the at least one second freewheel 51a, 51b forms a unidirectional coupling advantageously functioning by obstacle. In other words, this unidirectional coupling includes at least one element able to drive a first mobile by constituting an obstacle to it, such as a pawl, a hook, a leaf spring or a mobile pinion. This type of unidirectional coupling is advantageously very robust and able to withstand very numerous reversals of the rotation direction of the winding mobile mass 60, with a low dead angle and a low sensitivity to pollution that might degrade its performance. On the other hand, it may have some sensitivity to wear during high rotation speeds induced by manual winding (in the absence of a first freewheel 40 as in this embodiment). This is in particular the case when the freewheels are directly engaged with the winding mobile mass. Alternatively, the reverser 50 may include at least one mobile pinion, that is to say a pinion movable between:
In the embodiment represented the first freewheel 40 advantageously functions:
The elements 43 of the freewheel are blocking elements. These blocking elements may advantageously be made of ceramic, in particular technical ceramic.
As already mentioned, the automatic winding kinematic chain 200 enables winding of a spring of the barrel 20 thanks to the energy induced by the movements of the winding mobile mass 60. Winding can be directional, that is to say effective whatever the direction of rotation of the winding mobile mass 60. The winding mobile mass 60 can pivot in a ball bearing on the frame of the movement or on a frame of the automatic winding module. The automatic winding chain 200 includes a plurality of mobiles including, from the upstream side (the winding mobile mass) to the downstream side (the barrel):
The various mobiles or elements are preferably mechanically connected to one another by meshing with one another. The mechanical connections may be direct or indirect. In the case of two elements indirectly connected to one another, one or more intermediate wheels may be provided between the elements. These intermediate wheels may contribute to producing an optimised transmission ratio between the elements.
One or more intermediate wheels may be disposed between:
The reverser 50 and the first freewheel 40 are advantageously mechanically connected to one another, in particular directly connected by direct meshing of an output of the reverser 50, or of the outputs of the reverser 50, with an input of the first freewheel 40.
An input of the reverser 50, or inputs of the reverser 50, and the winding mobile mass 60 are advantageously mechanically connected directly to one another, in particular directly connected by of an input of the reverser 50 or inputs of the reverser 50 meshing with teeth 61 on the winding mobile mass 60.
It is preferable if:
The various axes A60, A51a, A51b, A40, A30 and A20 are preferably parallel to one another.
The winding mobile mass, the unidirectional couplings 51a, 51b, the first freewheel 40, the ratchet driver 30 and the barrel 20 are preferably guided in rotation on the frame of the movement and/or on a frame of the automatic winding module.
The transmission or reduction ratio between the winding mobile mass 60 and the ratchet 21 is of the order of 110 to 180. In other words, it is necessary for the winding mobile mass 60 to turn 110 to 180 times to induce rotation of the ratchet 21 by one turn.
The timepiece 400 preferably includes the winding stem 10 connected to the ratchet 21 by a manual winding chain 100 in order to enable manual winding or arming of the spring of the barrel 20.
The reverser 50 preferably includes two pawl freewheels 51a, 51b. The reverser 50 is advantageously directly engaged with the winding mobile mass 60, in particular with teeth 61 on the winding mobile mass 60, so that the dead angle of the reverser 50 relative to the winding mobile mass 60 is as small as possible, thus optimising automatic winding performance. Furthermore, in the embodiment shown the inputs 52a, 52b of the two second freewheels are advantageously rotationally coupled to one another directly by meshing. Only one input 52a of the two inputs 52a, 52b is connected directly in rotation to the winding mobile 60 by meshing therewith.
Alternatively, the two outputs of the two second freewheels may be rotationally coupled to one another directly by meshing and the two inputs may each be rotationally coupled directly to the winding mobile mass by meshing therewith.
The pawl freewheels 51a, 51b respectively include a pawl carrier wheel 52a, 52b, a cover 56a, 56b and two pawls 53a, 53b. The pawls 53a, 53b pivot on the pawl carrier wheel 52a, 52b and/or the cover 56a, 56b. Cooperation of the cover 56a, 56b and the pawl carrier wheel 52a, 52b enables retention of the pawls 53a, 53b in the at least one second freewheel 51a, 51b. The pawls 53a, 53b are advantageously made of ceramic, in particular technical ceramic.
The pawls 53a, 53b are designed to cooperate with a sawtooth toothed wheel 54a, 54b secured to a pinion 55a, 55b. The toothed wheel 54a, 54b is able to pivot relative to the pawl carrier wheel 52a, 52b. The respective asymmetric shapes of the pawls 53a, 53b and the toothed wheel 54a, 54b enable unidirectional coupling. The toothed wheels 54a, 54b are for example made of ceramic, in particular technical ceramic. The operation of a freewheel of this type is described for example in the document EP3285123A1.
In the automatic winding chain 200 the wedging type first freewheel 40 is advantageously a ball type freewheel 40 directly engaged with the reverser 50, between the latter and the ratchet 21. The first freewheel 40 more particularly includes a wheel 41 that is directly engaged with at least one of the two pinions 55a, 55b of the two second wheels 51a, 51b. The first freewheel 40 is moreover engaged with the ratchet driver 30 via a pinion 45 of the first freewheel 40.
In the automatic winding chain 200 the first freewheel 40 disposed in this way in direct engagement with the reverser 50 obtains the benefit of a dead angle relative to the winding mobile mass 60 that is minimised. With a disposition of this kind, after manual winding fewer turns of the winding mobile mass are therefore needed to make up said dead angle and to render automatic winding effective again. Moreover, this disposition of the first freewheel 40 also makes it possible to reduce the transmission torque that said first freewheel must withstand compared to a disposition of the first freewheel 40 close to the ratchet 21, for example.
In this embodiment, like a ball bearing, the first freewheel 40 includes six balls 43 guided in a sliding or rolling track 44 defining the interface between a wheel 41 and a ring 46 secured to the pinion 45. Furthermore, in a first configuration, upon immobilisation of the wheel 41 and the ring 46 to secure them to one another, the balls also make it possible, in a second configuration, to guide rotation of the ring 46 relative to the wheel 41 or to participate in such guidance.
Each ball 43 takes its place in a housing provided with an inclined plane machined in a separator 42. The separator 42 may comprise a plurality of parts, here three parts. Said inclined plane participates in the unidirectional coupling. In fact, in a first so-called engagement relative rotation direction the balls cooperate with the inclined plane so as to become wedged in the housing and to constrain the wheel 41 to rotate with the ring 46 by means of the separators 42. The latter are then tighten again around the ring 46, like a radial engagement or a radial action brake on the ring 46. In a second so-called free relative rotation direction (second direction opposite the first direction), the balls are out of reach of the portions of the inclined planes adapted to wedge the balls 43 so as to disengage the wheel 41 from the ring 46 and enable relative rotation between these two elements.
During an automatic winding phase the ball type first freewheel 40 is in an engaged configuration or goes from a disengaged configuration to an engaged configuration. In fact, during this phase the reverser 50 still drives the wheel 41 in the engagement relative direction, i.e. the anticlockwise direction in
The first freewheel 40 remains engaged whatever the direction of rotation of the winding mobile mass 60. In fact, when the winding mobile mass 60 turns in the clockwise direction in
The pinion 55a associated with the pawl carrier wheel 52a meshed directly with the winding mobile mass 60 is able to turn freely in the clockwise direction (wheel 51a disengaged) and the pinion 55b associated with the pawl carrier wheel 52b meshed indirectly with the winding mobile mass 60 turns in the clockwise direction (wheel 51b engaged). Here it follows that the wheel 41 turns in the anticlockwise direction. The two second freewheels 51a, 51b are respectively disengaged and engaged.
When the winding mobile mass 60 turns in the anticlockwise direction in
The pinion 55b associated with the pawl carrier wheel 52b meshed indirectly with the winding mobile mass 60 is able to turn freely in the clockwise direction (wheel 51b disengaged) and the pinion 55a associated with the pawl carrier wheel 52a meshed directly with the winding mobile mass 60 turns in the clockwise direction (wheel 51a engaged). It follows that the wheel 41 turns in the anticlockwise direction. Here the two second wheels 51a, 51b are respectively engaged and disengaged.
As mentioned above, the reverser advantageously includes two second freewheels 51a, 51b. The output of the reverser therefore turns in the same given direction whatever the direction of rotation of the input of the reverser.
Only manual winding enables disengagement of the first freewheel 40 via the driver 30 and the pinion 45.
During a manual winding phase the first freewheel is disengaged and the reverser 50 is advantageously disengaged from the driver 30 by the first freewheel 40. In fact, in this phase the pinion 45 and the ring 46 secured together are driven in the free relative direction (the anticlockwise rotation direction of the pinion 45 relative to the wheel 41 in
This advantageously results in a sensation and a winding torque on the winding stem 10 equivalent to a movement with no automatic winding system whilst preserving the second wheels 51a, 51b of the reverser 50.
As the first freewheel 40 is directly engaged with the reverser 50, the automatic winding torque generated by the winding mobile mass 60 that said first freewheel has to withstand is lower than if that first freewheel were arranged close to the ratchet 21. This arrangement therefore offers a more favourable transmission ratio and advantageously enables use of an optimised ball type first freewheel 40 with much better performance in terms in particular of dead angle and intrinsic friction than those known from the prior art used to disengage an automatic winding chain.
During manual winding it is preferable to guarantee that the first freewheel 40 is disengaged at all times and consequently for it to be impossible to load the reverser 50. To achieve this, the torque for disengaging the first freewheel 40 mounted on the reverser 50 must be lower than the disengagement torque of the latter. Now, the low transmission ratio between:
achieved by the solutions described above and the use of a first freewheel 40 make it possible to guarantee a very low disengagement torque whatever the speed of rotation. A freewheel functioning by wedging, such as a ball type first freewheel 40, advantageously offers a very low disengagement torque.
The dead angle at the first freewheel 40 has no or little influence on manual winding performance. The dead angle of the first freewheel 40 is the maximum angle that the wheel 41 must travel relative to the ring 46 before the wheel 41 and the ring 46 are again secured to one another.
However, if the ratchet 21 is immobilised by a ratchet pawl after manual winding automatic winding is effective only once the dead angle of the first freewheel 40 has been caught up. Consequently, the first movements of the winding mobile mass 60 will serve only to make up said dead angle, leading to momentary ineffective automatic winding.
The type of first freewheel 40 adopted and the architecture proposed here enable this disadvantage to be limited. In fact, the intrinsic functioning of the first freewheel 40 advantageously enables a very small dead angle to be achieved. Furthermore, given that the first freewheel 40 is directly engaged with the reverser 50, it is advantageously located where the transmission ratio with the winding mobile mass 60 is the lowest.
Consequently, the dead angle of the first freewheel 40 is more rapidly caught up by the movements of the winding mobile mass 60 than if the first freewheel 40 had been placed closer to the ratchet 21.
Once the first freewheel 40 is engaged, the dead angle of the first freewheel 40 no longer has any influence on the performance of automatic winding, because it then remains constantly engaged until the next manual winding.
A first reduction ratio between:
The automatic winding chain 200 preferably includes a first reduction chain extending from the winding mobile mass 60 to the first freewheel 40, in particular the wheel 41, having a second reduction ratio less than 6, or even less than 5, or even less than 4.
The automatic winding chain 200 preferably includes a second reduction chain extending from the first freewheel 40, in particular of the pinion 45, to the ratchet 21 of the barrel 20 having a third reduction ratio greater than 20, or even greater than 25, or even greater than 30.
The ratio of the second reduction ratio to the first reduction ratio is preferably less than 3, or even less than 2, or even less than 1.
The solution described uses a pawl or obstacle type reverser directly engaged with a winding mobile mass and advantageously includes a unidirectional bearing of ball freewheel type enabling optimisation of performance and the sensations of the user during manual winding.
The proposed solution finally enables disengagement of an automatic winding chain with the aid of a freewheel advantageously functioning by wedging, such as a unidirectional ball bearing. The freewheel is advantageously directly engaged with the reverser equipped with freewheels functioning by obstacle, such as pawl type freewheels. This solution enables the benefit to be obtained of a low and constant manual winding torque. In fact, as disengagement is achieved with no oscillating components, the variation of torque and wear problems are solved. Furthermore, this unidirectional bearing enables the benefit to be obtained of a low dead angle that can be caught up by a much lower number (of the order of 5 to 8 times lower) of winding mobile mass turns than in the known solutions, thanks also to arranging it as close as possible to the reverser.
The connections, in particular the teeth, adapted to cooperate directly with upstream elements in the automatic winding chain 200 are or constitute inputs and the connections, in particular the teeth, adapted to cooperate directly with elements situated downstream in the automatic winding chain 200, are or constitute outputs.
In a series assembly the input of one element is connected to the output of a preceding element or upstream element and the output of the element is connected to the input of a following or downstream element.
| Number | Date | Country | Kind |
|---|---|---|---|
| 22209734.7 | Nov 2022 | EP | regional |
